Thank you for all, when very file sketch show message "Compiling File Done" when loading file having message "loading Problem" I have suspect board having problem! Earlier I have same experience on Arduino Uno then replaced board solve problem.
Yes I have selected "Arduino Nano" installed driver and selected com port. Thanks Rajkumar

Just want to say thanks again for sharing this. It helped me confirm a suspicion that my speed was drifting a little . You could hear it on sustained notes . Readings would vary from 33.22 to 33.45 or so in a seemingly periodic fashion. Strip down and clean of everything and oiling the motor has now got it perfect. Only the last digit bobbles a bit say 0.002 each way . Without this tool I would never have managed to correct this for certain. Tremendous.

Hi I have solve problem loading "Tacho" sketch file to Arduino Nano with LCD 16x 2 12c module. The problem is "Processor selection" I was selected earlier "ATmega328P" then solved by I select ATmega328P (old Bootloader) find below screenshot. Now working perfect so Turntable Tachometer meter can work on Nano or Uno with LCD 16x2 12c module. Thanks Rajkumar

Hi, guys
my first post here
Alexander posted a thread about this tach at lencoheaven (with link to original thread here) and i tried to build it but failed. Could you be so kind to help finding out what's wrong with my tach?
I got a Chinese Uno, installed microchip CH340G driver (instead of FT232RL), connected Uno with LCD, downloaded the last version of the script and i now i can see the "RPM ---" text at LC display. Unfortunately, i got four pins opto sensor instead of three and it's got marks A0, D0 addition to GND and VCC. I tried to connect A0 to pins 3 and 2 (A2 and A3 on Arduino Uno board) with no results. When i move my finger neaby the sensor, its diode blinks but it's not resulted on changing RPM on LCD. Any ideas how to connect a four pins sensor correctly to the Uno board? or may be some changes it the sketch file too? Thank you, guys

I'm not familiar with the opto module you have, but my guess is that AO is an analog output and DO is a digital output. You should verify that one or both of these pins goes to ground when it senses the mark on the platter (it should stay at ground if you stop the platter in this position). Use a DC voltmeter to determine this.

This (one) output should be connected to digital input 3 on the Arduino PCB. Pin 2 on the Arduino is a test point OUTPUT and should not have anything connected to it.

This (one) output should be connected to digital input 3 on the Arduino PCB. Pin 2 on the Arduino is a test point OUTPUT and should not have anything connected to it.

Follwing your advice i connected DO to pin3 of digital inputs, got no results and unpluged the Arduino power supply. When i turned it on a while later, it has started working. Magic, practically
Thank you! Now i need to solder the capacitor